[#785] Update requests to 2.25, required for Python 3.12

[nodet]

In order to use Python 3.12, one needs requests to be at least at 2.25.
I checked that

python -m venv --prompt "linkchecker" venv
source venv/bin/activate
pip install hatchling hatch-vcs -r requirements-min.txt
hatchling build --hooks-only
python --version
python -m linkcheck

works fine for all of Python versions 3.9.15, 3.10.6, 3.11.6, 3.12.0 and 3.12.1.
They work fine as well using requirements.txt instead of requirements-min.txt.

[cjmayo]

requirements-min.txt is only used for CI with the oldest version of Python we support, currently 3.9. And reflects the minimum API versions we need (ish, not least because it is a relatively new invention).

requirements.txt is also used by the CI. When a user installs they will be using pyproject.toml, which does duplicate the same requirements. But if not installed the latest versions of dependencies will be downloaded.

User instructions are documented in:
https://linkchecker.github.io/linkchecker/install.html

If someone was using an environment with requests 2.24 then maybe if we updated pyproject.toml this would help. But 2.25.0 was released in November 2020, before we declared LinkChecker v10.

I would definitely merge this PR in October 2027 (if Python stick to their current schedule). Is there something I have missed?

[nodet]

I was a bit confused by hatchling and hatch-vcs being necessary to code on LinkChecker (e.g. to run the tests) but not being included in requirements.txt, but I understand now that the latter is designed for the users, not the developers.

I don't think there's anything you missed, thanks for the answer.